Method and apparatus for controlling ue for cellular iot service in 5g mobile communication system

ABSTRACT

A method performed by an access and mobility management function (AMF), the method comprising receiving, from a User Equipment (UE), a first message including capability information related to a periodic registration timer, setting a periodic registration timer indication based on the capability information, and transmitting, to the UE, a second message including the periodic registration timer indication.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/792,001,filed Feb. 14, 2020, now Pat. No. 11,206,629, which is based on andclaims priority under 35 U.S.C. 119 to Korean Patent Application No.10-2019-0017623, filed Feb. 15, 2019 and Korean Patent Application No.10-2019-0090672, filed Jul. 26, 2019 in the Korean Intellectual PropertyOffice, the disclosures of which are herein incorporated by reference intheir entireties.

BACKGROUND 1. Field

In the detailed description of embodiments of the disclosure, a radioaccess network of which the 5G network standard is defined by 3^(rd)generation partnership projection (3GPP), new RAN (NR) corresponding toa core network, and a packet core (5G system, 5G core network, or NGcore (next generation core)) will be mainly discussed, but the mainsubject of the disclosure with a slight change can be applied to othercommunication systems having a similar technical background within arange without departing from the scope of the disclosure, which can bemade by the determination of a person skilled in the art.

A CIoT service of the 5G system may support a function in which a UEtransmits data to a core network through a non access stratum (NAS)message and the core network transmits the data to an external datanetwork and a function in which data transmitted by the UE istransferred to an external server through a network exposure function(NEF).

Further, the 5G system may provide a service for factory automation,which may be called industrial IoT. Robots and other equipment used forfactory automation may communicate through a cellular network and maybelong to IoT equipment in a wide range. Such devices require datacommunication sensitive to time. For example, the device should transmitstatus information and a command message to another device through anetwork within 10 ms and may be configured to provide or receiverequired status information at a specific time.

For convenience of description, the disclosure uses terms and namesdefined in the 3rd-generation partnership project long-term evolution(3GPP LTE) standard. However, the disclosure is not limited to the termsand names, but may be equally applied to a system following anotherstandard.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a ‘Beyond 4G Network’ or a‘Post LTE System’. The 5G communication system is considered to beimplemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, soas to accomplish higher data rates. To decrease propagation loss of theradio waves and increase the transmission distance, the beamforming,massive multiple-input multiple-output (MIMO), full dimensional MIMO(FD-MIMO), array antenna, an analog beam forming, large scale antennatechniques are discussed in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud radio access networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,coordinated multi-points (CoMP), reception-end interference cancellationand the like. In the 5G system, hybrid FSK and QAM modulation (FQAM) andsliding window superposition coding (SWSC) as an advanced codingmodulation (ACM), and filter bank multi carrier (FBMC), non-orthogonalmultiple access(NOMA), and sparse code multiple access (SCMA) as anadvanced access technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofeverything (IoE), which is a combination of the IoT technology and thebig data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “security technology” have been demanded forIoT implementation, a sensor network, a machine-to-machine (M2M)communication, machine type communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing information technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, machine type communication (MTC), andmachine-to-machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud radioaccess network (RAN) as the above-described big data processingtechnology may also be considered to be as an example of convergencebetween the 5G technology and the IoT technology.

With the recent development of long-term evolution (LTE) andLTE-advanced, a method and an apparatus for efficiently controlling a UEfor a cellular IoT service in a 5G mobile communication system areneeded.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

The disclosure proposes a method of supporting the following twoservices to support a CIoT service in a 5G mobile communication system.

In one of the IoT-related services in the 5G mobile communicationsystem, if there are scheduled downlink data to be transmitted to a UEat a specific time, for example, at 9 a.m. Monday or at 12 a.m. everymorning, a 3^(rd) party application server (hereinafter, referred to asan AS) may provide the corresponding schedule information to a mobilecommunication network, and the mobile communication network may preparefor transmission of data to the UE at the corresponding time. The mobilecommunication network may perform an operation of controlling the UE tobe reachable at the time according to the schedule information orproviding resources for data transmission. The disclosure proposes amethod by which the corresponding UE maintains a connected state withthe mobile communication network at the scheduled data transmission timein the mobile communication network. The method is valid for IoT UEstransitioning to a state in which the UEs cannot be reachable the mobilecommunication network in order to reduce power consumption. The UEperforming a specific operation to reduce power consumption may be a UEwhich turns on a model and wakes up only when there is data to betransmitted (for example, MICO mode) or a UE which negotiates with themobile communication network to reduce power consumption and cannot bepaged by the network for a predetermined time.

In order to transmit data to the UE according to the schedule requestedfrom the 3^(rd) party AS which provides an application service, the 5Gsystem may support an operation for connecting the UE to the network atthe time according to the corresponding schedule in the disclosure.Accordingly, the UE may wake up and access the network at the specifictime through the access to the 3GPP network alone without any additionaloperation for controlling the operation of the UE.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for certain words and phrases are provided throughout thispatent document. Those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosure and its advantages,reference is now made to the following description taken in conjunctionwith the accompanying drawings, in which like reference numeralsrepresent like parts:

FIGS. 1A and 1B illustrate a method by which an AMF or an SMF acquiresschedule information of scheduled data transmission, triggers aregistration procedure of a UE, and negotiates a policy for running aperiodic registration timer with the UE through the registrationprocedure according to an embodiment of the disclosure;

FIGS. 2A and 2B illustrate an operation in which an AMF negotiatescapability for a policy of operating a periodic registration timer witha UE through a registration procedure and a method by which the AMF oran SMF acquires schedule information for scheduled data transmission andthen triggers a registration procedure of the UE according to anembodiment of the disclosure;

FIG. 3 illustrates a structure of a UE according to an embodiment of thedisclosure; and

FIG. 4 illustrates a structure of a network entity according to anembodiment of the disclosure.

DETAILED DESCRIPTION

FIGS. 1A through 4, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

Hereinafter, embodiments of the disclosure will be described in detailin conjunction with the accompanying drawings. In the followingdescription of the disclosure, a detailed description of known functionsor configurations incorporated herein will be omitted when it may makethe subject matter of the disclosure rather unclear. The terms whichwill be described below are terms defined in consideration of thefunctions in the disclosure, and may be different according to users,intentions of the users, or customs. Therefore, the definitions of theterms should be made based on the contents throughout the specification.

The advantages and features of the disclosure and ways to achieve themwill be apparent by making reference to embodiments as described belowin detail in conjunction with the accompanying drawings. However, thedisclosure is not limited to the embodiments set forth below, but may beimplemented in various different forms. The following embodiments areprovided only to completely disclose the disclosure and inform thoseskilled in the art of the scope of the disclosure, and the disclosure isdefined only by the scope of the appended claims. Throughout thespecification, the same or like reference numerals designate the same orlike elements.

Entities in the disclosure will be described below.

A user equipment (UE) is connected to a radio access network (RAN) andaccesses a device that performs a mobility management function of a corenetwork device of 5G. In the disclosure, the device is called an accessand mobility management function (AMF). This refers to a function or adevice that performs both access to the RAN and mobility management ofthe UE. An SMF is a name of a network function corresponding to asession management function. The AMF may be connected to the SMF and mayroute a message related to a session for the UE to the SMF. The SMF isconnected to a user plane function (UPF), allocates user plane resourcesto be provided to the UE, and establishes a tunnel for transmitting databetween a base station and the UPF. An NRF is an abbreviation of anetwork repository function and corresponds to a function of storinginformation on NFs installed in a mobile communication service providernetwork and informing of the information. The NRF may be connected toall NFs, and each NF may perform a registration procedure in the NRFwhen starting operating in a service provider network and thus allow theNRF to recognize that the corresponding NF is operating within thenetwork. The NEF is an abbreviation of a network exposure function andserves to expose a function and a service inside the mobilecommunication service provider network to the outside. Accordingly, theNEF is connected to an external application server (AS) and performs afunction of transmitting an event or information generated by the NFwithin the network or transmitting an event or information which the ASmakes a request for to the NF. A UDM plays the same role as an HSS of a4G network and is an abbreviation of unified data management. The UDMstores subscription information of the UE or context used by the UEwithin the network.

As a technology that is a background of the disclosure, a function forsupporting a CIoT service is described below.

Scheduled Downlink Data Communication Service: a 5G mobile communicationnetwork may receive schedule information of a scheduled downlink datatransmission time for a specific terminal or group from a 3^(rd) partyAS. The 3^(rd) party AS may be an application server existing outside 5Gmobile communication network elements. For example, if industrial IoTsupports data transmission using a 5G mobile communication system, anapplication server operating for the an industrial IoT service may beconsidered as a 3^(rd) party AS from a viewpoint of the 5G mobilecommunication system. In another example, a service provider providingan IoT service may issue a command to IoT UEs at a regular time ordesignate a scheduled communication time to perform a software update ata specific time. The 3^(rd) party AS may provide an available time forwhich the UE accesses a 3G network to receive data or scheduleinformation (that is, a time for which the UE is reachable the network,can receive paging, or should be in a connected state) through an“Expected UE Behaviour” Provisioning API. The scheduled information mayinclude a plurality of pieces of schedule information. For example, aplurality of schedules such as 9 o'clock every Monday, 0 p.m. everymorning, 10 hours from the present time, and 20 minutes from the presenttime may be provided.

When the UE desires to use a power saving state (a state in which the UEis not reachable the network to reduce power consumption, that is, astate in which the UE does not perform a network connection-relatedoperation, such as not monitoring a paging channel), the networkreceiving the schedule information may be configured to find the UE(such that the UE is reachable) at the scheduled communication time. Forexample, the scheduled communication time may be compared to a time atwhich the UE periodically informs the network of reachability (forexample, a periodic registration request timer) and the next periodicregistration request time of the UE may be configured to be suitable forthe scheduled communication time. In another example, if the scheduledcommunication time is earlier than the next periodic registrationrequest time of the UE, a power saving function of the UE may not beallowed, and thus the UE may be reachable at the corresponding time.

FIGS. 1A and 1B illustrate a method by which an AMF 120 or an SMF 140acquires schedule information of scheduled data transmission, triggers aregistration procedure of a UE 100, and negotiates a policy for runninga periodic registration timer with the UE 100 through the registrationprocedure according to an embodiment of the disclosure.

The UE 100 may perform an operation (for example, IDLE mode DRX) ofstopping monitoring a paging channel (for example, MICO mode, PSM in 4Gsystem) or monitoring a paging channel only in a specific time intervalin order to reduce power consumption. To this end, the UE 100 shouldnegotiate with the AMF 120 through a registration procedure. In thedisclosure, negotiation of the UE 100 about the use of a MICO mode isdescribed by way of example. However, this may comprehensively includeother functions for negotiation of the UE 100 with the AMF 120 to reducepower consumption. For example, other functions may include 5G PowerSaving Mode, 5G discontinuous reception (DRX), and 5G Extended DRX. Thedisclosure describes the MICO mode for convenience. The MICO mode refersto a mode in which, when the UE 100 enters an IDLE mode, the UE 100cannot be found in the 5G network, that is, a mode in which the UE 100moves to an unreachable state without monitoring of all paging channels.When the UE 100 should transmit data or should performing signaling, orafter a periodic registration request timer configured by the networkexpires, the UE 100 accesses again the 5G network. Accordingly, thenetwork cannot wake up the UE 100 before a registration requestprocedure performed at a periodic time configured by the UE 100.

The following information is proposed according to an embodiment of thedisclosure. A periodic registration request time indicates a time atwhich the UE 100 should periodically make a registration request. Thisis allocated to the UE 100 by the AMF 120. A periodic registrationrequest timer is a timer operating according to the periodicregistration request time and operates in each of the UE 100 and the AMF120. Further, the disclosure proposes a policy for the operation of theperiodic registration request timer of the UE 100 (for convenience,referred to as a periodic registration request timer policy). This meansan indicator(or indication) indicating that when the UE 100 operates theperiodic registration request timer, the UE 100 continuously operatesthe periodic registration request timer without stopping the same duringtransition from CM-IDLE to CM-Connected. Alternatively, the periodicregistration timer running policy may mean an indicator indicatingstarting the corresponding timer from the moment the UE 100 receivesallocation of the periodic registration request timer and continuouslyoperating the periodic registration request timer without stopping thesame during transition from CM-Connected to CM-IDLE or from CM-Connectedto CM-IDLE. Further, an indicator indicating whether the periodicregistration timer running policy is a one-shot policy (that is, apolicy released after one application) or a continuously applied policy(a policy for continuously maintaining the periodic registration requesttimer policy before the AMF provides a new policy) may be additionallyincluded. If the indicator indicating continuously operating theperiodic registration request timer without stopping the same, such asthe periodic registration timer running policy, is included, the UE 100continuously operates the corresponding time during transition fromCM-IDLE to CM-Connected, still operates the timer while the connectedstate is maintained, and continuously operates the timer until the timerexpires. Further, the UE starts the corresponding timer from the momentthe UE 100 receives allocation of the periodic registration requesttimer along with the indicator and continuously operates the periodicregistration request timer without stopping the same during transitionfrom CM-Connected to CM-IDL or from CM-Connected to CM-IDLE. If theindicator indicating that the periodic registration timer running policyis a one-shot policy is included, the UE 100 may release the applicationof the corresponding policy after the periodic registration requesttimer expires. That is, the normal operation (stopping the timer duringtransition from CM-IDLE to CM-Connected or restarting the timer from atimer initial value during transition from CM-Connected to CM-Idle) maybe performed as the operation of the periodic registration timer.

A 3^(rd) party application server or an AS may configure a scheduledcommunication time in the 5G network. The configuration may be performedas the AS directly transmits a message to a UDM or the AMF 120 or as theAS transmits information to the UDM through the NEF and the UDMtransmits the corresponding information to the AMF 120 or the SMF 140through UE context. The AS may configure the scheduled communicationtime to be a plurality of schedules and transmit the same. For example,the AS may transmit a plurality of pieces of schedule information suchas 0 o'clock every day, 12:30 every day, 20 minutes later, or anabsolute time value (for example, UTC 20:00, Jul. 10, 2018) indicating atimer later than now through the 5G network.

The disclosure premises that the scheduled communication time is storedin context of the UE 100 in the UDM and the AMF 120 or the SMF 140acquires the scheduled communication time in steps 101 and 102 a. The AFmay provide corresponding information through the NEF, the NEF maytransmit the same to the UDM, and the UDM may classify and store thecorresponding information as session management context of the UE 100.Alternatively, the NEF may directly transmit the scheduled communicationtime for the specific UE 100 to the AMF 120 or the SMF 140 and the AMF120 or the SMF 140 may acquire the corresponding value according tosteps 101 and 102 a. Since the scheduled communication time is providedfrom a 3^(rd) party to the UDM for a specific UE 100 indicated by anexternal ID or an external group ID, the UDM may store the scheduledcommunication time value in SM context according to each external ID orexternal group ID of the UE 100. This is because the UE 100 may haveseveral external IDs or external group IDs. Alternatively, the scheduledcommunication time may be provided from a 3^(rd) party to the UDM as avalue for a data network name (DNN) for a specific UE 100 indicated byan external ID or an external group ID. In this case, the UDM may storethe scheduled communication time in SM context according to a DNN valuefor each external ID or external group ID of the UE 100. This is tosupport the case in which the UE 100 has several external IDs orexternal group IDs or in which subscriber information is configured suchthat the UE 100 uses several DNNs for an NIDD service. That is, thescheduled communication time may be configured in subscriber informationof the UDM for each UE, and a plurality of scheduled communication timemay be configured for each external ID or external group ID or for eachof the external ID/external group ID and the DNN.

Step 102 b is an operation performed when the SMF 140 acquires thescheduled communication time information from the UDM through SM contextfor the UE 100 or the SMF 140 acquires the same from the NEF, that is,after step 102 a. The SMF 140 may identify when downlink data of thecorresponding UE 100 is transmitted on the basis of the scheduledcommunication time. Since the UE 100 should reach the 5G network at thecorresponding time, the SMF 140 may transmit a message indicatingreachability of the UE 100 to the AMF 120 performing mobility managementof the UE 100. This is one of APIs provided by the AMF 120 and isdifferent from the name of step 102 b in the drawing, but may correspondto a message proposed by the disclosure if the message is to provide thescheduled communication time of the specific UE 100 to the AMF 120 bythe SMF 140. For example, the message may be transmitted using an APIprovided by the SMF 140, such as Nsmf_PDU Session Update SM Context. TheSMF 140 may include an ID of the UE 100 (an ID by which the AMFidentifies the UE, for example, a subscription concealed identifier(SUCI), a subscription permanent identifier (SUPI corresponding to aconventional IMSI), or an external ID), the scheduled communication timeacquired in step 102 a, and a PDU session ID indicating a correspondingPDU session in step 102 b. A reason why the PDU session ID is includedis that, if the UE 100 uses data communication with several PDUsessions, the UE 100 may determine which PDU session should be activatedwhen the UE 100 transmits a service request and wakes up at thescheduled communication time. Further, the reason is to identify a PDUsession for the scheduled communication time by the AMF 120 if the UE100 uses data communication with several PDU sessions. If the AMF 120may receive several scheduled communication time values from a pluralityof SMFs or one SMF, the AMF 120 may identify the scheduled communicationtime values for respective PDU sessions on the basis of the PDU sessionID included in message step 102 b.

The AMF 120 recognizing the scheduled communication time for the UE 100through the message of step 102 b or step 101 may store the same incontext of the UE 100. Further, the AMF 120 may allocate a periodicregistration timer value on the basis thereof. The AMF 120 may determineto apply a periodic registration timer running policy to the UE 100 inorder to allow the UE 100 to wake up and access the network at thescheduled communication time. That is, the AMF 120 may not stop theperiodic registration timer when the UE 100 transitions from CM-IDLE toCM-Connected, continuously operate the periodic registration timer evenwhen the UE 100 is in the connected state, and perform the registrationprocedure when the periodic registration timer expires in the CM-IDLEstate of the UE 100 to allow the UE 100 to access the network and attachto the network at a time point at which scheduled communication isperformed.

The AMF 120 may perform step 103 to transmit the periodic registrationtime value and the periodic registration timer running policy accordingto the scheduled communication time, or may transmit the same to the UE100 when the UE 100 makes a request for an operation of escaping thereachable state from the network during a specific time, for example, arequest for a MICO mode through the registration procedure in order toreduce power consumption through the registration procedure.

The AMF 120 may recognize that the scheduled communication time isconfigured in the UE 100 according to step 101 or 102 b, andaccordingly, determine to control the periodic registration requesttimer value of the UE 100. Further, the AMF 120 may determine the policyfor the operation of the periodic registration request timer of the UE100. For example if the scheduled communication time for the UE 100 is aone-shot time, that is, if the scheduled communication time indicates aspecific time (UTC 12:00, 2019-02-12), the periodic registration requesttimer policy may be determined as a one-shot policy. In another example,if the scheduled communication time for the UE 100 is a regular time,that is, if the scheduled communication time is, for example, 9 a.m.every Monday or 12 p.m. every day, the periodic registration requesttimer policy may be determined as a continuously applied policy. The AMF120 may configure an indicator according thereto, which may betransmitted to the UE 100 during the registration procedure.

In order to make the UE 100 wake up at the scheduled communication time,the AMF 120 may perform a UE configuration update procedure in step 103to transmit the periodic registration timer to the UE 100 or to performthe registration procedure. This is to transmit the periodicregistration timer value according to the scheduled communication timeand the periodic registration timer running policy to the UE 100. TheAMF 120 may include the periodic registration time value and theperiodic registration timer running policy determined through theprocedure in a UE configuration update command message in step 103. Theperiodic registration timer running policy may be an indicatorindicating continuous operation of the periodic registration timerregardless of transition between CM-IDLE and CM-Connected.Alternatively, the periodic registration timer running policy may meanan indicator indicating starting the corresponding timer from the momentthe UE 100 receives allocation of the periodic registration requesttimer and continuously operating the periodic registration request timerwithout stopping the same during transition from CM-Connected to CM-IDLEor from CM-Connected to CM-IDLE. Further, an indicator indicatingwhether the corresponding periodic registration timer running policy isa one-shot policy or a policy that should be continuously maintained maybe included. The UE 100 may transmit a response message of the UEconfiguration update command transmitted by the AMF 120 and, at thistime, may acknowledge the application of the transmitted information.

Alternatively, the AMF 120 may perform only an operation for triggeringthe UE 100 to transmit a registration request instead of inserting theperiodic registration timer and the periodic registration timer runningpolicy information into the UE configuration update command message.Accordingly, the AMF 120 may insert an indicator indicating that theregistration procedure is needed into the UE configuration updatecommand message and transmit the message to the UE 100. At this time,the AMF 120 may also transmit an indicator indicating the UE 100 can usethe MICO mode. The UE 100 transmits a response message of the UEconfiguration update command transmitted by the AMF 120.

The UE 100 inserts an indicator indicating the UE will use the MICO modeinto a registration request message and transmits the message in step104. Step 104 may be performed as the operation according to step 103.That is, if the AMF 120 informs the UE 100 that the registrationprocedure is needed through the UE configuration update command messageof step 103, the registration procedure may be performed in step 104.Alternatively, step 104 may be performed because the UE 100 negotiateswith the AMF 120 in order to activate the MICO mode so as to reducepower consumption. In addition, step 104 may be a registration procedureaccording to movement of the UE 100 or a registration procedureperformed at a periodic time. Further, step 104 may be registrationprocedure by the UE 100 to synchronize a time with the network. Underother conditions, the UE 100 may perform all registration procedureswith the AMF 120.

The AMF 120 may determine whether to allow the UE 100 to execute theMICO mode in step 105. If the scheduled communication time for the UE100 arrives soon, the AMF 120 may not allow the UE 100 to execute theMICO mode such that the UE 100 continuously remains in the reachablestate without entering the MICO mode. If the scheduled communicationtime value for the UE 100 arrives sufficiently after the entry into theMICO mode of the UE 100, the AMF 120 may allow the UE 100 to execute theMICO mode such that the UE 100 enters the MICO mode and reduces powerconsumption.

The AMF 120 may configure, in the UE 100 to execute the MICO mode, aperiodic registration timer value which should be operated by thecorresponding UE 100 in step 106. This may be configured on the basis ofthe scheduled communication time value, and the AMF 120 may configure avalue indicating a little earlier time than the scheduled communicationtime. This is to consider a delay that may be generated when the UE 100accesses the network. Further, the AMF 120 may configure the periodicregistration timer running policy in order to allow the UE 100 to wakeup at the scheduled communication time and access the network. Thisrefers to an indicator indicating continuously operation of the periodicregistration request timer without stop during transition from CM-IDLEto CM-Connected. Further, an indicator indicating whether the periodicregistration timer running policy is a one-time policy (that is, apolicy released after one application) or a continuously applied policy(a policy for continuously maintaining the periodic registration requesttimer policy before the AMF provides a new policy) may be additionallyincluded.

The AMF 120 may transmit the periodic registration timer value and theperiodic registration timer running policy determined in step 106 alongwith the indicator indicating allowance of the MICO mode to the UE 100in step 107. The UE 100 receiving the same may determine continuousoperation of the periodic registration request timer without stop on thebasis of the periodic registration timer running policy in the receivedinformation when the UE transitions from CM-IDLE to CM-Connected.Accordingly, the UE 100 may operate the periodic registration timeraccording to the periodic registration timer value received after theregistration procedure ends (that is, after step 108 in which theregistration complete message is transmitted to the AMF 120).Alternatively, the UE 100 may operate the corresponding timer afterreceiving the registration accept, identifying the periodic registrationrequest timer included in the registration accept, and identifyingwhether the corresponding timer is applied to the periodic registrationtimer running policy. The UE 100 may continuously operate thecorresponding timer even during the transition from CM-IDLE toCM-Connected, still operate the timer while the UE maintains theconnected state, and continuously operate the timer until the timerexpires. If the indicator indicating that the periodic registrationtimer running policy is a one-time policy is included, the UE 100releases the application of the corresponding policy after the periodicregistration request timer expires. That is, the normal operation(stopping the timer during transition from CM-IDLE to CM-Connected orreinitiating the timer from a timer initial value during transition fromCM-Connected to CM-Idle) may be performed as the operation of theperiodic registration timer.

The UE 100 may inform of the completion of the registration procedurethrough step 108. According to an embodiment of the disclosure, the UE100 may transmit acknowledgement indicating that the periodicregistration timer running policy received in step 107 will be appliedto the AMF 120 through a registration complete message. The AMF 120receiving the acknowledgment may determine that the UE 100 applies theperiodic registration timer running policy and, accordingly, operate theperiodic registration timer on the AMF 120 side. Since the UE 100transmitted the acknowledgement indicating the application of theperiodic registration timer running policy, the AMF 220 may continuouslyoperate the corresponding timer even when the connection state of the UE100 transitions from CM-IDLE to CM-Connected, still operate the timerduring the connected state, and continuously operate the timer until thetimer expires like the operation of the UE. The AMF 120 may execute thetimer right after the registration complete message is received. Theperiodic registration timer value operated on the AMF 120 side may be alittle larger than a value allocated to the UE 100. For example, theperiodic registration timer value may be 5-minutes larger. This isbecause a time delay may be generated due to an error of a radiocondition during the periodic registration procedure performed by the UE100 and is to prevent the AMF 120 from determining that the UE 100implicitly detaches if the AMF 120 cannot receive the registrationrequest message from the UE 100 after the periodic registration timerexpires for a time due to the error. As the AMF 120 operates the timerhaving a little larger value, the AMF 220 may correctly perform theregistration procedure without determining that the UE 100 is implicitlydetached even though there is a delay of the registration procedure ofthe UE 100 due to the error of the radio condition.

According to an embodiment of the disclosure, the UE 100 may nottransmit acknowledgement indicating that the periodic registration timerrunning policy received in step 107 will be applied to the AMF 120through a registration complete message. That is, if the UE 100 does notsupport the periodic registration timer running policy or determines notto use the same, the UE 100 may not transmit the registration completemessage to the AMF 120, and even though the registration completemessage is transmitted, the UE 100 may not insert acknowledgementindicating that the periodic registration timer running policy isapplied. The AMF 120 receiving the registration complete message maydetermine that the UE 100 does not support or use the periodicregistration timer running policy. Accordingly, the AMF 120 may operatethe periodic registration timer according to the normal operation. Sincethe UE 100 does not support or apply the periodic registration timerrunning policy, the UE 100 operates the periodic registration timeraccording to the normal operation.

After completing the registration procedure, the UE 100 allowed toexecute the MICO mode may transition to the IDLE state and then operatein the MICO mode. Further, if it is determined to apply the periodicregistration timer running policy, the UE 100 may operate the periodicregistration timer according thereto. The network cannot page the UE 100while the UE 100 is in the MICO mode. If the UE 100 operates a DRX cyclehaving a long value rather than the MICO mode, the network cannot pagethe UE 100 while the UE 200 is in a DRX sleep cycle. However, if thereis data or signaling to be transmitted to the network, the UE 100 maywake up anytime and communicate with the network in step 109. If thereis a newly configured scheduled communication time value, the AMF 120may perform an operation for updating the periodic registration timerand the periodic registration timer running policy in the UE 100 througha UE configuration update procedure (same as step 103).

According to an embodiment of the disclosure, if the configured periodicregistration timer expires in step 110 a, the UE 100 makes aregistration request in order to wake up and access the network andtransition to the connected state. The AMF 120 receiving theregistration request switches the state of the UE 100 to the connectedstate. According to an embodiment of the disclosure, the AMF 120 mayinform the SMF 140 for a PDU session or a DNN configuring the scheduledcommunication time of reachability of the UE 100 and activate a userplane of the UE 100 or a data path of the UE 100 so as to transmitscheduled downlink data.

In step 110 a, the UE 100 may be in the CM-Connected state. That is, theperiodic registration timer may have expired while the UE 100 accessesthe network and transmit/receive data for the data transmissionoperation. In this case, the UE 100 has already accessed the network,and thus does not need to perform the registration procedure for networkaccess at a time point at which the timer has expired. According to anembodiment of the disclosure, the UE 100 performs the followingoperation. First, if the periodic registration timer running policy isconfigured and accordingly the periodic registration timer is operated,the UE 100 may determine not to perform the periodic registrationprocedure in the connected state when the timer expires on the basis ofthe determination. Since the timer has expired, the UE 100 does notrestart the periodic registration timer until the UE 200 transitions tothe CM-IDLE state. After transmitting and receiving data, the UE 100transitions to the CM-IDLE state and then operates the periodicregistration timer again. Alternatively, if the UE 100 is in theCM-connected state at a time at which the timer expires, the UE 100 mayimmediately restart the timer by applying the preset periodicregistration timer and the periodic registration timer running policytherefor without performing the periodic registration procedure. Inother words, if the timer expires in the connected state, the UE maycontinuously apply the periodic registration timer running policy untilnext timer expiration without waiting for transition to CM-IDLE. At thistime, if the UE 100 receives an indicator indicating whether theperiodic registration timer running policy is a one-shot policy or acontinuously used policy from the AMF 120, the UE 200 may perform thefollowing operation according to the indicator. If the periodicregistration timer running policy is a one-shot policy, the UE 100releases the periodic registration timer running policy after theperiodic registration timer expires in the connected state. That is, theUE 200 does not apply the periodic registration timer running policy anymore. If the periodic registration timer running policy is acontinuously applied policy, the UE 100 continuously maintains theperiodic registration timer running policy after the periodicregistration timer expires in the connected state. Accordingly, afterthe timer expires in the CM-connected state, the timer may be restartedand operated according to the periodic registration timer runningpolicy. Second, the UE 100 may perform the periodic registrationprocedure in the connected state. If the periodic registration timerrunning policy is configured and accordingly the periodic registrationtimer is operated even though the timer has expired and the UE 100 is inthe connected state, the UE 100 may determine not to perform theperiodic registration procedure when the timer expires in the connectedstate on the basis of the determination. Through the procedure, the UE100 may receive reallocation of the periodic registration timer, receivea new periodic registration timer running policy, or identify no moreapplication of the periodic registration timer running policy. If theAMF 120 does not insert the periodic registration timer running policyinto a registration accept message, the UE 100 may determine that theperiodic registration timer running policy is not applied any more.

If the periodic registration timer operated on the AMF side for the UE100 expires, the AMF 120 may perform a UE configuration update procedurein step 103 according to an embodiment of the disclosure when thecorresponding UE 100 is in the connected state and when the periodicregistration timer running policy is being applied. This is to updatethe periodic registration timer value according to the scheduledcommunication time and the periodic registration timer running policyinformation in the UE 100. If the scheduled communication time is notvalid any more, that is, if the AMF 120 determines that there is noconfigured scheduled communication time or there is no need to apply thescheduled communication time any more, the AMF 220 may inform the UE 100of release of the periodic registration timer running policy through theUE configuration update procedure. In another example, if there is avalid scheduled communication timer configured after the present time,the AMF 120 may configure a periodic registration timer according to thecorresponding scheduled communication time and determine to apply theperiodic registration timer running policy. The AMF 120 may insert theperiodic registration timer value determined through the procedure andthe periodic registration timer running policy into a UE configurationupdate command message. The periodic registration timer running policymay be an indicator indicating continuous operation of the periodicregistration timer regardless of transition between CM-IDLE andCM-Connected. Further, an indicator indicating whether the correspondingperiodic registration timer running policy is a one-shot policy or apolicy that should be continuously maintained may be included. The UE100 may transmit a response message of the UE configuration updatecommand transmitted by the AMF 120 and, at this time, may acknowledgethe application of the transmitted information. If the AMF 120determines not to apply the periodic registration timer running policyany more, the AMF 220 may insert an indicator indicating release of theperiodic registration timer running policy into the UE configurationupdate command message. After determining that the UE is a UE to whichthe periodic registration timer running policy is applied, the AMF 120may insert the indicator indicating release of the periodic registrationtimer running policy into the UE configuration update command messagetransmitted to the corresponding UE 100. The UE 100 may transmit aresponse message of the UE configuration update command transmitted bythe AMF 120 and, at this time, may acknowledge the application of thetransmitted information.

Alternatively, the AMF 120 may perform only an operation for triggeringthe UE 100 to transmit a registration request instead of inserting theperiodic registration timer and the periodic registration timer runningpolicy information into the UE configuration update command message.Accordingly, the AMF 120 may insert an indicator indicating that theregistration procedure is needed into the UE configuration updatecommand message and transmit the message to the UE 100. At this time,the AMF 120 may also transmit an indicator indicating the UE 100 can usethe MICO mode. The UE 100 may transmit a response message of the UEconfiguration update command transmitted by the AMF 120. Thereafter, theUE 100 performs the registration procedure in step 104.

Step 110 b indicates generation of downlink data at the scheduledcommunication time as arranged. After receiving downlink data from thedata network, a UPF 160 may inform the SMF 140 of the reception of thedownlink data and activate a data path through which the data can betransmitted to the UE 100. Such a process may follow a NW-initiatedservice request. According to the NW-initiated service request, thenetwork pages the UE 100, and the UE 100 having woken up transmits aservice request and transitions to the connected state.

The UE 100 may transmit a registration request message to the AMF 220 instep 111 according to the determination operation of step 110 a. The AMF120 receiving the registration request message may maintain theconnection of the UE 100 for a predetermined time until a downlink datanotification for the UE 100 is received. If the UE 100 returns to theIDLE state, the UE 200 may become unreachable again. If the downlinkdata for the UE 100 arrives while the connection of the UE 100 ismaintained and the SMF 140 informs the AMF 120 of activation of the datapath for the corresponding UE 100, the AMF 120 may perform a procedurefor activating the corresponding data path. In another example, the UE100 may also insert information on a PDU session for activating the datapath into “PDU Session to be Activated” along with the registrationrequest in step 111. The insertion is performed because the UE 100applied the periodic registration timer running policy and it isdetermined that there is scheduled communication. Accordingly, it is toactivate the data path by making a request for activating thecorresponding PDU session. This has an effect of omitting a procedure inwhich the SMF 140 informs the AMF 120 of arrival of the downlink data.The AMF 120 receiving the arrival of the downlink data may trigger theSMF 140 for the corresponding PDU session to activate the data path.After the data path for transmitting data to the UE 100 is activated bythe three operations, the data may be transmitted to the UE 100 in step112.

FIGS. 2A and 2B an operation in which an AMF 220 negotiates capabilityfor a policy of operating a periodic registration timer with a UE 200through a registration procedure and a method by which the AMF 220 or anSMF 240 acquires schedule information for scheduled data transmissionand then triggers a registration procedure of the UE according to anembodiment of the disclosure.

The UE 200 may perform an operation (for example, IDLE mode DRX) ofstopping monitoring a paging channel (for example, MICO mode, PSM in 4Gsystem) or monitoring a paging channel only in a specific time intervalin order to reduce power consumption. To this end, the UE 200 shouldnegotiate with the AMF 220 through a registration procedure. In thedisclosure, negotiation of the UE 200 about the use of a MICO mode isdescribed by way of example. However, this may comprehensively includeother functions for negotiation of the UE 200 with the AMF 220 to reducepower consumption. For example, other functions may include 5G PowerSaving Mode, 5G DRX, and 5G Extended DRX. The disclosure describes theMICO mode for convenience. The MICO mode refers to a mode in which, whenthe UE 200 enters an IDLE mode, the UE 200 cannot be found in the 5Gnetwork, that is, a mode in which the UE 100 moves to an unreachablestate without monitoring of all paging channels. If the UE 200 shouldtransmit data or should performing signaling, or after a periodicregistration request timer configured by the network expires, the UE 100accesses again the 5G network. Accordingly, the network cannot wake upthe UE 100 before a registration request procedure performed at aperiodic time configured by the UE 200.

The following information is proposed according to an embodiment of thedisclosure. A periodic registration request time indicates a time atwhich the UE 200 should periodically make a registration request. Thisis allocated to the UE 200 by the AMF 220. A periodic registrationrequest timer is a timer operating according to the periodicregistration request time value and operates in each of the UE 200 andthe AMF 220. Further, the disclosure proposes a policy for the operationof the periodic registration request timer of the UE 200 (forconvenience, referred to as a periodic registration request timerpolicy). This means an indicator indicating that when the UE 200operates the periodic registration request timer, the UE 200continuously operates the periodic registration request timer withoutstopping the same during transition from CM-IDLE to CM-Connected.Further, an indicator indicating whether the periodic registration timerrunning policy is a one-time policy (that is, a policy released afterone application) or a continuously applied policy (a policy forcontinuously maintaining the periodic registration request timer policybefore the AMF provides a new policy) may be additionally included. Ifthe indicator indicating continuously operating the periodicregistration request timer without stopping the same when the UEtransitions from the CM-IDLE state to the CM-Connected state through theperiodic registration timer running policy is included, the UE 200continuously operates the corresponding time during transition fromCM-IDLE to CM-Connected, still operates the timer while the connectedstate is maintained, and continuously operates the timer until the timerexpires. Alternatively, the UE 200 may start the corresponding timerfrom the moment the UE 200 receives allocation of the periodicregistration request timer and continuously operate the periodicregistration request timer without stopping the same during transitionfrom CM-Connected to CM-IDL or from CM-Connected to CM-IDLE. If theindicator indicating that the periodic registration timer running policyis a one-time policy is included, the UE 200 releases the application ofthe corresponding policy after the periodic registration request timerexpires. That is, the normal operation (stopping the timer duringtransition from CM-IDLE to CM-Connected or restarting the timer from atimer initial value during transition from CM-Connected to CM-Idle) maybe performed as the operation of the periodic registration timer.

A 3rd party application server or an AS may configure a scheduledcommunication time in the 5G network. The configuration may be performedas the AS directly transmits a message to a UDM or the AMF 220 or as theAS transmits information to the UDM through the NEF and the UDMtransmits the corresponding information to the AMF 220 or the SMF 240through UE context. The AS may configure the scheduled communicationtime to be a plurality of schedules and transmit the same. For example,the AS may transmit a plurality of pieces of schedule information suchas 0 o'clock every day, 12:30 every day, 20 minutes later, or anabsolute time value (for example, UTC 20:00, Jul. 10, 2018) indicating atimer later than now through the 5G network.

The UE 200 may insert an indicator indicating the UE will use the MICOmode into a registration request message and transmit the message instep 201. Further, according to an embodiment of the disclosure, the UE200 may also insert and transmit an indicator indicating whether the UE200 is able to support the periodic registration timer running policy.The UE 200 may indicate whether the UE can support a function ofcontinuously operating the periodic registration timer while the UEtransitions from CM-IDLE state to the CM-Connected state and while theCM-Connected state is maintained through the periodic registration timerrunning policy, that is, the indicator. If the UE 200 inserts theindicator into the message, the AMF 220 receiving the indicator maydetermine that the UE 200 supports the corresponding function.Similarly, if the UE 200 does not insert the indicator into the message,the AMF 220 receiving the registration request message may determinethat the UE 200 does not support the corresponding function. Step 201may be performed as the operation according to step 213. That is, if theAMF 220 informs the UE 200 that the registration procedure is neededthrough the UE configuration update command message of step 213, theregistration procedure may be performed in step 201. Alternatively, step201 may be performed because the UE 200 negotiates with the AMF 120 inorder to activate the MICO mode so as to reduce power consumption. Inaddition, step 201 may be a registration procedure according to movementof the UE 200 or a registration procedure performed at a periodic time.Further, step 201 may be registration procedure by the UE 200 tosynchronize a time with the network. Under other conditions, the UE 200may perform all registration procedures with the AMF 220.

The AMF 220 may determine whether to allow the UE 200 to execute theMICO mode in step 202. If the scheduled communication time for the UE200 arrives soon, the AMF 220 may not allow the UE 200 to execute theMICO mode such that the UE 200 continuously remains in the reachablestate without entering the MICO mode. If the scheduled communicationtime for the UE 200 arrives sufficiently after the entry into the MICOmode of the UE 200, the AMF 220 may allow the UE 200 to execute the MICOmode such that the UE 100 enters the MICO mode and reduces powerconsumption.

The AMF 220 determining to allow the UE 200 to execute the MICO mode instep 202 may configure a periodic registration timer value that shouldbe operated by the corresponding UE 200 according to the scheduledcommunication time configured in the UE 200. Further, the periodicregistration timer running policy may be determined. At this time,according to an embodiment of the disclosure, the AMF 220 may determinewhether to apply the periodic registration timer running policy to theUE 200 on the basis of an indicator indicating capability for theperiodic registration timer running policy in the message of step 201received from the UE 200. That is, if the UE 200 inserts the indicatorinto the message, the AMF 220 receiving the indicator may determine thatthe UE 200 supports the corresponding function. Similarly, if the UE 200does not insert the indicator into the message, the AMF 220 receivingthe registration request message may determine that the UE 200 does notsupport the corresponding function. Alternatively, if the indicatoritself indicates the presence of capability for the periodicregistration timer running policy, it may be determined that the UE 200supports the corresponding function. Alternatively, if the indicatoritself indicates the absence of capability for the periodic registrationtimer running policy, it may be determined that the UE 200 does not usethe corresponding function. The AMF 220 may determine the periodicregistration time on the basis of the scheduled communication timervalues, and configure a value indicating a time little earlier than thescheduled communication time. This is to consider a delay that may begenerated when the UE 200 accesses the network. Further, the AMF 220 mayconfigure the periodic registration timer running policy in order toallow the UE 200 to wake up at the scheduled communication time andaccess the network. This refers to an indicator indicating continuouslyoperation of the periodic registration request timer without stop duringtransition from CM-IDLE to CM-Connected. Alternatively, the indicatormay be an indicator indicating operation of the periodic registrationtimer immediately upon receipt (that is, after receiving a registrationaccept message and identifying periodic registration timer and periodicregistration timer running policy information included the registrationaccept message) and continuous operation of the periodic registrationrequest timer without stopping when the UE transitions from CM-Connectedto CM-IDLE or from CM-Connected to CM-IDLE. Further, an indicatorindicating whether the periodic registration timer running policy is aone-time policy (that is, a policy released after one application) or acontinuously applied policy (a policy for continuously maintaining theperiodic registration request timer policy before the AMF provides a newpolicy) may be additionally included.

The AMF 220 may transmit the periodic registration timer value and theperiodic registration timer running policy determined in step 203 alongwith the indicator indicating allowance of the MICO mode to the UE 200in step 204. The UE 200 receiving the same may determine continuousoperation of the periodic registration request timer without stop on thebasis of the periodic registration timer running policy in the receivedinformation when the UE transitions from CM-IDLE to CM-Connected.Accordingly, the UE 200 may operate the periodic registration timeraccording to the periodic registration timer value received after theregistration procedure ends. That is, the UE 200 may operate thecorresponding timer after receiving the registration accept, identifyingthe periodic registration request timer included in the registrationaccept, and identifying whether the corresponding timer is applied tothe periodic registration timer running policy. The UE 200 maycontinuously operate the corresponding timer even during the transitionfrom CM-IDLE to CM-Connected, still operate the timer while the UEmaintains the connected state, and continuously operates the timer untilthe timer expires. If the indicator indicating that the periodicregistration timer running policy is a one-time policy is included, theUE 200 may release the application of the corresponding policy after theperiodic registration request timer expires. That is, the normaloperation (stopping the timer during transition from CM-IDLE toCM-Connected or reinitiating the timer from a timer initial value duringtransition from CM-Connected to CM-Idle) may be performed as theoperation of the periodic registration timer. The AMF 220 may executethe timer after transmitting the registration accept message to the UE200. The periodic registration timer value operated on the AMF side maybe a little larger than a value allocated to the UE 200. For example,the periodic registration timer value may be 5-minutes larger. This isbecause a time delay may be generated due to an error of a radiocondition during the periodic registration procedure performed by the UE200 and is to prevent the AMF 220 from determining that the UE 200 isimplicitly detached if the AMF 220 cannot receive the registrationrequest message from the UE 200 after the periodic registration timerexpires for a time due to the error. As the AMF 220 operates the timerhaving a little larger value, the AMF 220 may correctly perform theregistration procedure without determining that the UE 200 is implicitlydetached even though there is a delay of the registration procedure ofthe UE 200 due to the error of the radio condition.

The UE 200 may inform of the completion of the registration procedurethrough step 205. This step may be omitted. According to an embodimentof the disclosure, the UE 200 may transmit acknowledgement indicatingthat the periodic registration timer running policy received in step 204will be applied to the AMF 220 through a registration complete message.The AMF 220 receiving the acknowledgment may determine that the UE 200applies the periodic registration timer running policy and, accordingly,operate the periodic registration timer on the AMF side. Since the UE200 transmitted the acknowledgement indicating the application of theperiodic registration timer running policy, the AMF 220 may continuouslyoperate the corresponding timer even when the connection state of the UE200 transitions from CM-IDLE to CM-Connected, still operate the timerduring the connected state, and continuously operate the timer until thetimer expires like the operation of the UE.

After completing the registration procedure, the UE 200 allowed toexecute the MICO mode may transition to the IDLE state and then operatein the MICO mode. Accordingly, the periodic registration timer isoperated. If the UE 200 determines to apply the periodic registrationtimer running policy may operate the periodic registration timer beforetransitioning to the IDLE state, that is, after receiving the periodicregistration timer running policy and receiving the periodicregistration timer value therefor. The network cannot page the UE 200while the UE 200 is in the MICO mode. If the UE 200 operates a DRX cyclehaving a long value rather than the MICO mode, the network cannot pagethe UE 200 while the UE 200 is in a DRX sleep cycle. However, if thereis data or signaling to be transmitted to the network, the UE 200 maywake up anytime and communicate with the network in step 206. If thereis a newly configured scheduled communication time value, the AMF 220may perform an operation for updating the periodic registration timerand the periodic registration timer running policy in the UE 200 througha UE configuration update procedure.

According to an embodiment of the disclosure, if the configured periodicregistration timer expires in step 207 a, the UE 200 makes aregistration request in order to wake up and access the network andtransition to the connected state. The AMF 220 receiving theregistration request switches the state of the UE 200 to the connectedstate. According to an embodiment of the disclosure, the AMF 220 mayinform the SMF 240 for a PDU session or a DNN configuring the scheduledcommunication time of reachability of the UE 200 and activate a userplane of the UE 200 or a data path of the UE 200 so as to transmitscheduled downlink data.

In step 207 a, the UE 200 may be in the CM-Connected state. That is, theperiodic registration timer may have expired while the UE 200 accessesthe network and transmit/receive data for the data transmissionoperation. In this case, the UE 200 has already accessed the network,and thus does not need to perform the registration procedure for networkaccess at a time point at which the timer has expired. According to anembodiment of the disclosure, the UE 200 perform the followingoperation. First, if the periodic registration timer running policy isconfigured and accordingly the periodic registration timer is operated,the UE 200 may determine not to perform the periodic registrationprocedure when the timer expires in the connected state on the basis ofthe determination. Since the timer has expired, the UE 200 does notrestart the periodic registration timer until the UE 200 transitions tothe CM-IDLE state. After transmitting and receiving data, the UE 200transitions to the CM-IDLE state and then operates the periodicregistration timer again. Alternatively, if the periodic registrationtimer running policy is configured and accordingly the periodicregistration timer is operated, the UE 200 may restart the correspondingtimer immediately from a time at which the periodic registration timerexpires when the timer expires in the CM-connected state. That is, theUE 200 may immediately start the timer without waiting for transition tothe CM-IDLE state. If the periodic registration timer expires when theUE 200 to which the periodic registration timer running policy isapplied is in the CM-connected state, the AMF 220 may also restart theperiodic registration timer immediately from the expiration time. Atthis time, if the UE 200 receives an indicator indicating whether theperiodic registration timer running policy is a one-shot policy or acontinuously used policy from the AMF 220, the UE 200 may perform thefollowing operation according to the indicator. If the periodicregistration timer running policy is a one-shot policy, the UE 200releases the periodic registration timer running policy after theperiodic registration timer expires in the connected state. That is, theUE 200 does not apply the periodic registration timer running policy anymore. If the periodic registration timer running policy is acontinuously applied policy, the UE 200 continuously maintains theperiodic registration timer running policy after the periodicregistration timer expires in the connected state. Accordingly, afterthe timer expires in the CM-connected state, the timer may be restartedand operated according to the periodic registration timer runningpolicy. Second, the UE 200 may perform the periodic registrationprocedure in the connected state. If the periodic registration timerrunning policy is configured and accordingly the periodic registrationtimer is operated even though the timer has expired and the UE 200 is inthe connected state, the UE 200 may determine not to perform theperiodic registration procedure when the timer expires in the connectedstate on the basis of the determination. Through the procedure, the UE200 may receive reallocation of the periodic registration timer, receivea new periodic registration timer running policy, or identify no moreapplication of the periodic registration timer running policy. If theAMF 220 does not insert the periodic registration timer running policyinto a registration accept message, the UE 200 may determine that theperiodic registration timer running policy is not applied any more.

If the periodic registration timer operated on the AMF side for the UE200 expires, the AMF 220 may perform a UE configuration update procedurein step 213 according to an embodiment of the disclosure when thecorresponding UE 200 is in the connected state and when the periodicregistration timer running policy is being applied. This is to updatethe periodic registration timer value according to the scheduledcommunication time and the periodic registration timer running policyinformation in the UE 200. If the scheduled communication time is notvalid any more, that is, if the AMF 220 determines that there is noconfigured scheduled communication time or there is no need to apply thescheduled communication time any more, the AMF 220 may inform the UE 200of release of the periodic registration timer running policy through theUE configuration update procedure. In another example, if there is avalid scheduled communication timer configured after the present time,the AMF 220 may configure a periodic registration timer according to thecorresponding scheduled communication time and determine to apply theperiodic registration timer running policy. The AMF 220 may insert theperiodic registration timer value determined through the procedure andthe periodic registration timer running policy into a UE configurationupdate command message. The periodic registration timer running policymay be an indicator indicating continuous operation of the periodicregistration timer regardless of transition between CM-IDLE andCM-Connected. Further, an indicator indicating whether the correspondingperiodic registration timer running policy is a one-shot policy or apolicy that should be continuously maintained may be included. The UE200 may transmit a response message of the UE configuration updatecommand transmitted by the AMF 220 and, at this time, may acknowledgethe application of the transmitted information. If the AMF 220determines not to apply the periodic registration timer running policyany more, the AMF 220 may insert an indicator indicating release of theperiodic registration timer running policy into the UE configurationupdate command message. After determining that the UE is a UE to whichthe periodic registration timer running policy is applied, the AMF 220may insert the indicator indicating release of the periodic registrationtimer running policy into the UE configuration update command messagetransmitted to the corresponding UE 200. The UE 200 may transmit aresponse message of the UE configuration update command transmitted bythe AMF 220 and, at this time, may acknowledge the application of thetransmitted information.

Alternatively, the AMF 220 may perform only an operation for triggeringthe UE 200 to transmit a registration request instead of inserting theperiodic registration timer and the periodic registration timer runningpolicy information into the UE configuration update command message.Accordingly, the AMF 220 may insert an indicator indicating that theregistration procedure is needed into the UE configuration updatecommand message and transmit the message to the UE 200. At this time,the AMF 220 may also transmit an indicator indicating that the UE 200can use the MICO mode. The UE 200 transmits a response message of the UEconfiguration update command transmitted by the AMF 220. Thereafter, theUE 200 may perform the registration procedure in step 204.

Step 207 b indicates generation of downlink data at the scheduledcommunication time as arranged. After receiving downlink data from thedata network, a UPF 260 may inform the SMF 240 of the reception of thedownlink data and activate a data path through which the data can betransmitted to the UE 200. Such a process may follow a NW-initiatedservice request. According to the NW-initiated service request, thenetwork pages the UE 200, and the UE 200 having woken up transmits aservice request and transitions to the connected state.

The UE 200 may transmit a registration request message to the AMF 220 instep 208 according to the determination operation of step 207 a. The AMF220 receiving the registration request message may maintain theconnection of the UE 200 for a predetermined time until a downlink datanotification for the UE 200 is received. If the UE 200 returns to theIDLE state, the UE 200 may become unreachable again. If the downlinkdata for the UE 200 arrives while the connection of the UE 200 ismaintained and the SMF 240 informs the AMF 220 of activation of the datapath for the corresponding UE 200, the AMF 220 may perform a procedurefor activating the corresponding data path. In another example, the UE200 may also insert information on a PDU session for activating the datapath into “PDU Session to be Activated” along with the registrationrequest in step 208. The insertion is performed because the UE 200applied the periodic registration timer running policy and thus it isdetermined that there is scheduled communication, and accordingly is toactivate the data path by making a request for activating thecorresponding PDU session. This has an effect of omitting a procedure inwhich the SMF 240 informs the AMF 220 of arrival of the downlink data.The AMF 220 receiving the arrival of the downlink data may trigger theSMF 240 for the corresponding PDU session to activate the data path.After the data path for transmitting data to the UE 200 is activated bythe three operations, the data may be transmitted to the UE 200 in step209.

The scheduled communication time is stored in context of the UE 200 inthe UDM, and thus the AMF 220 or the SMF 240 acquires the scheduledcommunication time in steps 210 and 211. The AF may providecorresponding information through the NEF, the NEF may transmit the sameto the UDM, and the UDM may classify and store the correspondinginformation as session management context of the UE 200. Alternatively,the NEF may directly transmit the scheduled communication time for thespecific UE 200 to the AMF 220 or the SMF 240 and the AMF 220 or the SMF240 may acquire the corresponding value according to steps 210 and 211.Since the scheduled communication time is provided from a 3^(rd) partyto the UDM for a specific UE 200 indicated by an external ID or anexternal group ID, the UDM may store the scheduled communication time inSM context according to each external ID or external group ID of the UE200. This is because the UE 200 may have several external IDs orexternal group IDs. Alternatively, the scheduled communication time maybe provided from a 3^(rd) party to the UDM as a value for a data networkname (DNN) for a specific UE 200 indicated by an external ID or anexternal group ID. In this case, the UDM may store the scheduledcommunication time in SM context according to a DNN value for eachexternal ID or external group ID of the UE 200. This is to support thecase in which the UE 200 has several external IDs or external group IDsor in which subscriber information is configured such that the UE 200uses several DNNs for an NIDD service. That is, the scheduledcommunication time may be configured in subscriber information of theUDM for each UE, and a plurality of scheduled communication time may beconfigured for each external ID or external group ID or for each of theexternal ID/external group ID and the DNN.

Step 212 is an operation performed when SMF 240 acquires the scheduledcommunication time information from the UDM through SM context for theUE 200 or the SMF 240 acquires the same from the NEF, that is, afterstep 211. The SMF 240 may identify when downlink data of thecorresponding UE 200 is transmitted on the basis of the scheduledcommunication time. Since the UE 200 should reach the 5G network at thecorresponding time, the SMF 240 may transmit a message indicatingreachability of the UE 200 to the AMF 220 performing mobility managementof the UE 200. This is one of APIs provided by the AMF 220 and isdifferent from the name of step 212 in the drawing, but may correspondto a message proposed by the disclosure if the message is to provide thescheduled communication time of the specific UE 200 to the AMF 220 bythe SMF 240. For example, the message may be transmitted using an APIprovided by the SMF 240, such as Nsmf_PDU Session Update SM Context. TheSMF 240 may include an ID of the UE 200 (an ID by which the AMFidentifies the UE, for example, a subscription concealed identifier(SUCI), a subscription permanent identifier (SUPI corresponding to aconventional IMSI), or an external ID), the scheduled communication timeacquired in step 212 and a PDU session ID indicating a corresponding PDUsession in step 212. A reason why the PDU session ID is included isthat, when the UE 200 uses data communication with several PDU sessions,the UE 200 may determine which PDU session should be activated when theUE 100 transmits a service request and wakes up at the scheduledcommunication time. Further, the reason is to identify a PDU session forthe scheduled communication by the AMF 220 if the UE 200 uses datacommunication with several PDU sessions. If the AMF 220 may receiveseveral scheduled communication time values from a plurality of SMFs orone SMF, the AMF 220 may identify the scheduled communication timevalues for respective PDU sessions on the basis of the PDU session IDincluded in the message.

The AMF 220 recognizing the scheduled communication time for the UE 200through the message of step 212 or step 210 stores the same in contextof the UE 200. Further, the AMF 220 may allocate a periodic registrationtimer value on the basis thereof. The AMF 220 may determine to apply aperiodic registration timer running policy to the UE 200 in order toallow the UE 200 to wake up and access the network at the scheduledcommunication time. That is, the AMF 120 may not stop the periodicregistration timer when the UE 200 transitions from CM-IDLE toCM-Connected, continuously operate the periodic registration timer evenwhen the UE 200 is in the connected state, and perform the registrationprocedure when the periodic registration timer expires in the CM-IDLEstate of the UE 200 to allow the UE 200 to access the network and attachto the network at a time point at which scheduled communication isperformed. The AMF 220 may perform step 213 to transmit the periodicregistration time value and the periodic registration timer runningpolicy according to the scheduled communication time, or may transmitthe same to the UE 200 when the UE 200 makes a request for an operationof escaping the reachable state during a specific time, for example, arequest for a MICO mode through the registration procedure in order toreduce power consumption through the registration procedure of the UE200.

In step 213, the AMF 220 may determine to control the periodicregistration request timer value of the UE 200 according to thescheduled communication time configured in the UE 200. Further, the AMF120 may determine the policy for the operation of the periodicregistration request timer of the UE 200. That is, the AMF 120 maydetermine to apply a policy for continuously operating the periodicregistration request timer without stopping the same even though the UE200 transitions from CM-IDLE to CM-Connected. In another example, if thescheduled communication time for the UE 200 is a one-shot time, that is,if the scheduled communication time indicates a specific time (UTC12:00, 2019-02-12), the periodic registration request timer policy maybe determined as a one-shot policy. In another example, if the scheduledcommunication time for the UE 200 is a regular time, that is, if thescheduled communication time is, for example, 9 a.m. every Monday or 12p.m. every day, the periodic registration request timer policy may bedetermined as a continuously applied policy. The AMF 220 may configurean indicator according thereto, which may be transmitted to the UE 200during the registration procedure or the UE configuration updateprocedure.

In order to make the UE 200 wake up at the scheduled communication time,the AMF 220 may perform a UE configuration update procedure in step 213to transmit the periodic registration timer to the UE 200 or to performthe registration procedure. This is to transmit the periodicregistration timer value according to the scheduled communication timeand the periodic registration timer running policy to the UE 200. TheAMF 220 may insert the periodic registration timer value determinedthrough the step and the periodic registration timer running policy intothe UE configuration update command message in step 213. The periodicregistration timer running policy may be an indicator indicatingcontinuous operation of the periodic registration timer regardless oftransition between CM-IDLE and CM-Connected. Further, an indicatorindicating whether the corresponding periodic registration timer runningpolicy is a one-shot policy or a policy that should be continuouslymaintained may be included. The UE 200 may transmit a response messageof the UE configuration update command transmitted by the AMF 220 and,at this time, may acknowledge the application of the transmittedinformation.

Alternatively, the AMF 220 may perform only an operation for triggeringthe UE 200 to transmit a registration request instead of inserting theperiodic registration timer and the periodic registration timer runningpolicy information into the UE configuration update command message.Accordingly, the AMF 220 may insert an indicator indicating that theregistration procedure is needed into the UE configuration updatecommand message and transmit the message to the UE 200. At this time,the AMF 220 may also transmit an indicator indicating the UE 200 can usethe MICO mode. The UE 200 transmits a response message of the UEconfiguration update command transmitted by the AMF 220. The UE 200receiving a trigger for making the registration request performs theoperation according to step 201 of FIG. 2A.

FIG. 3 illustrates a structure of a UE according to an embodiment of thedisclosure.

Referring to FIG. 3, the UE may include a transceiver 310, a controller320, and a memory 330. In the disclosure, the controller may be definedas a circuit, an application-specific integrated circuit, or at leastone processor.

The transceiver 310 may transmit/receive a signal to/from anothernetwork entity. The transceiver 310 may receive, for example, systeminformation from the BS and receive a synchronization signal or areference signal.

The controller 320 may control the overall operation of the UE accordingto an embodiment proposed by the disclosure.

The memory 330 may store at least one piece of informationtransmitted/received through the transceiver 310 and informationgenerated through the controller 320.

FIG. 4 illustrates a structure of a network entity according to anembodiment of the disclosure.

Referring to FIG. 4, the BS may include a transceiver 410, a controller420, and a memory 430. In the disclosure, the controller may be definedas a circuit, an application-specific integrated circuit, or at leastone processor.

The transceiver 410 may transmit and receive a signal to and fromanother network entity and the UE. The transceiver 410 may transmit, forexample, system information to the UE and transmit a synchronizationsignal or a reference signal.

The controller 420 may control the overall operation of the BS accordingto an embodiment proposed by the disclosure.

The memory 430 may store at least one piece of informationtransmitted/received through the transceiver 410 and informationgenerated through the controller 420.

The embodiments of the disclosure described and shown in thespecification and the drawings have been presented to easily explain thetechnical contents of the disclosure and help understanding of thedisclosure, and are not intended to limit the scope of the disclosure.That is, it will be apparent to those skilled in the art that othermodifications and changes may be made thereto on the basis of thetechnical spirit of the disclosure. Further, the above respectiveembodiments may be employed in combination, as necessary. For example,the embodiments of the disclosure may be partially combined to operate abase station and a terminal.

Further, although various embodiments of the disclosure have beendescribed and shown in the specification and the drawings by usingparticular terms, the terms have been used in a general sense merely toeasily explain the technical contents of the disclosure and helpunderstanding of the disclosure, and are not intended to limit the scopeof the disclosure. It will be apparent to those skilled in the art that,in addition to the embodiments disclosed herein, other variants may beachieved on the basis of the technical spirit of the disclosure.

Although the present disclosure has been described with variousembodiments, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method by an Access and Mobility managementFunction (AMF) in a wireless communication system, the methodcomprising: receiving, from a User Equipment (UE), a first messageincluding capability information related to a periodic registrationtimer indication; determining whether to apply the periodic registrationtimer indication to the UE based on the capability information in thefirst message; transmitting, to the UE, a second message including theperiodic registration timer indication based on the determination;starting a periodic registration timer after completion of Registrationprocedure in case that the periodic registration timer indication isprovided; and restarting the periodic registration timer by applying theperiodic registration timer indication in case that the periodicregistration timer expires and the UE is in CONNECTED mode.